There are many situations in which it is desirable for furniture, grandstands, and the like to be easily assemblable and disassemblable for moving or storage. Various types of detachable joints have been proposed for use in collapsible furniture. These known joints tend to have a number of problems associated with them. Many of such joints are overly complex and expensive and lack versatility in the types of structures in which they can be used. Known detachable joint arrangements also tend to be relatively difficult and time consuming to assemble and disassemble. Another common problem is that the part of the joint tend to wear when the joint is assembled and disassembled, thus leading to a loosening of the joint and an overall decrease in the strength of the piece of furniture. Known detachable furniture joints also generally do not have any means of compensating for irregularities in the parts of the furniture being joined, such as irregularities on the outer surface of a vertical support member or the horizontal member to which the vertical support member is to be joined. Such irregularities can cause wobbliness in the joint and, thus, adversely affect the strength of the piece of furniture.
Joints which are apparently detachable and in which one end of a shaft engages a leg and the other end of the shaft extends through a corner brace are disclosed in U.S. Pat. No. 310,133, granted Dec. 30, 1884, to R. C. Haase; U.S. Pat. No. 2,386,201, granted Oct. 9, 1945, to J. A. Ferguson; U.S. Pat. No. 3,327,658, granted June 27, 1967, to K. D. Schreyer; and U.S. Pat. No. 3,572,787, granted Mar. 30, 1971, to G. L. Timmerman et al. In each of the joints disclosed in these four patents, the end of the shaft which extends through the corner brace is threaded and is engaged by a nut that is turned to pull the leg against side rails. U.S. Pat. No. 326,582, granted Sept. 22, 1885, to W. A. Osborn et al., discloses a joint in which opposite ends of a clamp are received into grooves in a table leg, end portions of two side rails are received into additional grooves in the leg, and a hook extending from the clamp extends through a corner brace and is engaged by a curved rotating wedge. U.S. Pat. No. 3,167,292, granted Jan. 26, 1965, to N. L. Meyerowitz, discloses a circular bracket for supporting a table top on a pole. The pole extends through the bracket and the table top and is secured in position by a flap inside the bracket which is urged against the pole by means of a thumb screw.
U.S. Pat. No. 509,618, granted Nov. 28, 1893, to G. C. Goodyear, discloses a fastening for a furniture leg. In the Goodyear arrangement, the ends of two side rails are received into grooves in the leg and a "clip" extends around the outer portion of the leg and through openings in the side rails. The two inner ends of the clip extend through a tie which forms a corner brace. The inner ends are threaded, and the clip is tightened around the leg by two nuts which engage the inner ends.
U.S. Pat. No. 3,280,767, granted Oct. 25, 1966, to B. Kahn, discloses knock-down metal shelving. In the shelving arrangement, each of the four corner posts is attached to each shelf by a joint which includes a metal ring that surrounds the post. A set screw extends through a corner piece and through the ring to bear against the post. A nut is turned to pull the ring into contact with the vertical flanges of the shelf to tighten the joint.
A shelf and corner post assembly is disclosed in U.S. Pat. No. 3,964,404, granted June 22, 1976, to F. F. Mueller et al. Further embodiments of the assembly are disclosed in U.S. Pat. No. 4,132,178, granted Jan. 2, 1979, to the same inventors. In the assembly, each corner post is urged against the inside surface of the perimeter of the shelf frame. A diagonal corner brace is secured to the frame. A U-shaped clip has upper and lower arms that straddle and abut the upper and lower surfaces of the brace. A screw is received through an opening in the U-shaped clip and threadedly engages the brace to urge the clip against the post and the post against the inner perimeter surface of the frame. In an alternative embodiment shown in FIGS. 9-11 of the later patent, the U-shaped clip is replaced by a cam locking lever carried by the diagonal brace.
U.S. Pat. No. 4,237,798, granted Dec. 9, 1980, to J. H. Welsch et al., discloses adjustable metal shelving. In the shelving, each of the four corner posts is attached to each shelf by means of a clamp. Each corner of the shelf is truncated and has a diagonal vertical surface. A brace member fits over the diagonal surface and is secured thereto by screws. The brace member forms a pocket with upper and lower walls which have arcuate seats that correspond in shape to the circumferential shape of the post. The U-shaped clamp member extends around the post with its opposite arms being received into the pocket formed by the brace member. The screws which connect the brace member to the truncated surface of the shelf also extend into the clamp member to pull the clamp member into engagement with the post and secure the post between the clamp and the arcuate seats formed by the brace member. The height and width of the clamp is approximately the same as the height and width of the pocket of the brace member to provide a substantially tight fit between the clamp and the pocket.
The above patents and the prior art that is cited therein should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.